Google grades every website on three technical metrics called Core Web Vitals. They sound intimidating, but each one answers a simple human question about your page. Here’s the plain-language version — and honest guidance on fixing costs.
The three metrics, in human terms
LCP — Largest Contentful Paint: “How fast does the main thing appear?” This measures how long until the biggest visible element (usually your hero image or headline) has loaded. Good is 2.5 seconds or faster. Slower than that and visitors feel the page is sluggish before they’ve read a word.
INP — Interaction to Next Paint: “How fast does the page react when I click?” This measures the delay between a user interacting (tapping a button, opening a menu) and the page visibly responding. Good is 200 milliseconds or faster. Poor INP is that frustrating feeling of clicking and nothing happening.
CLS — Cumulative Layout Shift: “Does stuff jump around while loading?” This measures unexpected movement — text shoving down as an image loads, a button jumping just as you tap it. Good is a score under 0.1. High CLS makes a site feel cheap and causes misclicks.
Why they matter
Two reasons. First, Google uses them as a ranking factor — better vitals can help you rank, poor ones hold you back. Second, and more importantly, they measure real user experience. A site that scores well simply feels good to use, and that shows up in conversions, not just rankings.
What typically goes wrong
- Slow LCP: oversized images, slow hosting, render-blocking scripts, no caching.
- Poor INP: heavy JavaScript doing too much work on the main thread.
- High CLS: images and ads without reserved space, fonts that swap and reflow text.
Roughly what fixing costs
Honest ranges — every site differs:
- Quick wins (image compression, caching, reserving image dimensions): often a few hours of work and a noticeable improvement. A cost-effective first pass.
- Moderate work (script optimisation, lazy-loading, font handling, cleaning up plugins): a small project, usually paying for itself in better rankings and conversions.
- Deep fixes (rebuilding a bloated theme, re-architecting a heavy JavaScript front end): a larger investment — sometimes the honest answer is that a lean rebuild costs less than endlessly patching a slow site.
Where to start
Run your site through Google’s PageSpeed Insights for a free baseline. Fix the quick wins first — they often move the needle enough to pass. Only invest in deep work if the fundamentals are genuinely broken.
Want a clear report on your vitals and a fixed quote to fix them? Get in touch.
